1. Field of the Invention
This invention relates generally to commodity bags, and more specifically to a sealable commodity bag including a venting means allowing for air to escape from the bag after closure.
2. Description of the Prior Art
Commodity bags are widely used in industry for storing a variety of dry powdery or granular products. Food products such as powdered milk and the like require a closure that resists moisture and contaminants from entering the bag. Most of the commodity bags commonly used for dry foods include an interior plastic bag or liner combined with several outer plies of paper. Such bags are formed by folding flat material into a tube with overlapping margins and sealing the margins together with heat seals or glues, then folding and sealing one end of the tube to form a bag, which is then similarly folded and sealed at the other end after filling. The multiple plies of paper with the plastic result in a very strong and burst resistant container that may be air tight.
One problem that arises from this type of container is that air and possible other gasses may be easily trapped within the bag along with the contents. Several condiment bags have been developed that allow air to escape after closure. Some of the methods used in these designs somewhat discourage moisture and contaminants from entering the bags.
Perry (U.S. Pat. No. 3,302,859) discloses a method allowing air to pass through crescent shaped holes in a bag. The most effective version of this bag locates the cuts, or vents, along the margin of overlapping materials and between two heat seals wherein the vents formed through one layer of the overlapping margins are misaligned with the vents formed through the opposing layer. The intention is that the opposing layer of material will lie against and thereby are off the vents once air is pressed from the bag. This design is problematic in that the flexibility and distortability of the plastic material, and the repeated handling of the bag all effect the reliability of this method especially where the contents can easily pass through the vents.
Kenan (U.S. Pat. No. 4,470,153) discloses an improvement in venting where a strip of paper or filter like material is sealed within the margin between two seals. The filter material is then incorporated into the end seals thereby creating a filtered path for air to pass. The practicality of this design comes into question as well as the ease of manufacturing. This design may also encourage moisture to enter the bag if the filter is absorbent.
Keppel (Pat. No. 4,550,441) provides a more practical and practiced method wherein channel formed between two heat seals along overlapping margins include distally separated vent holes formed through each of the overlapping layers, wherein one of the vent holes is formed through the inner layer (into the bag interior) and the other vent hole is formed through the outer layer. Air, contents, and contaminants must travel a course through the channel to enter or exit the bag. The relative effectiveness of this method is proven in practice, though the vent holes must be punctured through the bag, and the puncture holes are small and easily obstructed.
By careful examination of these methods, it should be clear that the further the distance that separates the vent holes, the more effective the method. It can also be concluded that the effectiveness of these methods to inhibit or prevent the entry of contaminants and moisture and the re-entry of air can be influenced by the distortions, movement, turning and positioning of the bag relative to gravitational and other forces to which the bag and it""s contents may be subjected.
What is needed is an improved vented bag that does not require punctured or cut holes through the bag surface.
What is also needed is a sealed bag with an improved means of venting which discourages or greatly inhibits the movement of moisture and particles through the venting means especially where the bag may be subjected to turning, handling and forces of nature.
It is an object of the present invention to provide an improved vented bag that does not require punctured or cut holes through the bag surface.
It is also an object of the present invention to provide a sealed bag with and improved means of venting the bag where a plurality of seals are included along the length of overlapping margins, and where the seals are non-continuous in that strategically located open spaces along the seals cause the seals to form a maze-shaped channel with at least one open space providing communication with the interior of the bag and at least one open space providing communication with the exterior of the bag.
Another object of the present invention is to provide a vented bag with a maze-shaped channel, or tortuous path, to allow communication between the interior and exterior of the bag wherein the maze-shaped channel forms a relatively long and multi-directional path which discourages or greatly inhibits the movement of moisture and particles through the channel especially where the bag may be subjected to turning, handling and forces of nature.
Furthermore, it is an object of the present invention to provide a bag such as a commodity bag that includes a relatively long and narrow maze-shaped channel allowing for the evacuation of air from the bag wherein the bag interior layer and included channel are manufactured from flexible plastic film and wherein the layers of film forming the channel will, in their natural state and after the evacuation of air from the channel, tend to lie flatly together thereby closing the channel to the re-entry of air into the channel.
Yet another object of the present invention is to disclose a method of manufacturing a vented bag with a plurality of non-continuous seals specifically spaced to form a maze-shaped channel that provides communication between the interior and the exterior of the bag. These and other objects and advantages will become apparent from the following drawings and description.
Briefly, a presently preferred embodiment of the present invention includes a vented bag including at least one rectangular sheet of substantially gas-impervious material having a top edge, a bottom edge opposite said top edge, and a first side edge folded over an opposite second side edge to form a tube. The tube has a longitudinal seam including at least first and second overlapping sheet portions joined together along a plurality of seal lines extending longitudinally from said top edge of said sheet to said bottom edge of said sheet. The bag is sealed to closure at one end of said tube. Each of the plurality of seal lines includes a discontinuity proximate one of the top and bottom edges of the sheet. The discontinuities in adjacent ones of the seal lines are disposed proximate opposites ones of the top and bottom edges of the sheet such that the plurality of seal lines, the discontinuities, and the first and second overlapping sheet portions form a tortuous channel providing communication between the interior of the bag and the exterior of the bag.
In an alternative embodiment, the starting material for the bags are tubular and the tortuous channel is disposed in the closure formed in at last one end thereof.
An important advantage of the present invention is that the maze-shaped channel, or tortuous path, allows communication between the interior and exterior of the bag wherein the maze-shaped channel discourages or greatly inhibits the movement of moisture and particles through the channel especially where the bag may be subjected to turning, handling, and forces of nature.
The foregoing and other objects, features, and advantages of the present invention will be apparent from the following detailed description of the preferred embodiment which makes reference to the several figures of the drawing.